API RP 934-A PDF

This recommended practice (RP) covers materials and fabrication requirements for new 2¼Cr and 3Cr steel heavy-wall pressure vessels for high-temperature, high-pressure hydrogen service. For this RP, “heavy-wall” is defined as a shell thickness of 4 in. (100 mm) or greater, and “high-temperature” is considered to be operating temperatures of 650 °F (345 °C) and up to a maximum design temperature where ASME Section II-D:2023 Table 5A defines the threshold time-dependent properties for the given material classification and in compliance with API 941. This RP applies to pressure vessels that are designed, fabricated, certified, and documented in accordance with ASME Section VIII, Division 2, Class 2, including Paragraph 3.4, Supplemental Requirements for Cr-Mo Steels, and ASME Code Case 2151, as applicable.

This RP applies to new heavy-wall pressure vessels in petroleum refining, petrochemical, and chemical facilities in which hydrogen or hydrogen-containing fluids are processed at elevated temperature and pressure.